Each of Patent Documents 1 and 2 discloses an in-vehicle system in which a plurality of electronic control units (hereinafter abbreviated as ECUs) are connected by a communication line to be capable of communicating data therebetween. The in-vehicle system is configured to be able to communicate data related to the diagnosis of the plurality of ECUs. The in-vehicle system is also configured to be able to transmit data to an external device provided outside a vehicle. For example, a configuration is known which outputs data related to diagnosis to an external device so as to support the diagnosis of a failure in a vehicle in a repair plant or the like.
An in-vehicle system includes a plurality of ECUs. However, each of the ECUs needs to provide its intrinsic control function of controlling equipment mounted in a vehicle. As a result, the ECU may take a long time to transmit data related to diagnosis to an external device.
On the other hand, the communication line of the in-vehicle system also needs to provide its intrinsic function of communicating data for controlling the vehicle. As a result, the communication line may take a long time to transmit/receive data related to diagnosis. In addition, from another viewpoint, it is undesirable that traffic on the communication line increases to transmit/receive data related to diagnosis.
From another perspective, the in-vehicle system and the external device should comply with a common communication standard to allow data communication therebetween. However, for the in-vehicle system and the external device, different communication standards may be selected and used by their manufacturers. For example, when the external device is provided by a general-purpose microcomputer, it is desirable that a general-purpose communication standard can be used. Therefore, the in-vehicle system is required to be compatible with a plurality of communication standards.    [Patent Document 1] JP-A-2003-87174    [Patent Document 2] JP-A-2011-203082 (corresponding to US 2011/0238262)